package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.CACHE_NULL_TTL;
import static com.hmdp.utils.RedisConstants.CACHE_SHOP_KEY;
import static com.hmdp.utils.RedisConstants.CACHE_SHOP_TTL;
import static com.hmdp.utils.RedisConstants.LOCK_SHOP_KEY;

/**
 * 缓存工具类
 */
@Component
@Slf4j
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;
    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }
    //存入数据，包含包含过期时间
    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }
    //存入数据包含逻辑过期时间
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期
        RedisData redisData=new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }
    //解决缓存穿透查询
    public <R,ID> R queryWithPassThrough(
            String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback,Long time, TimeUnit unit){
        //1.从redis中查询
        String  json = stringRedisTemplate.opsForValue().get(keyPrefix+id);
        //2.判断是否存在
        if(StrUtil.isNotBlank(json)){
            //3.存在，直接返回
            return JSONUtil.toBean(json, type);
        }
        // 命中是否是空值
        if(json!=null){
            //返回一个错误信息
            return null;
        }
        //4.不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        //5.不存在，返回错误
        if(r==null){
            // 将空值写入Redis
            stringRedisTemplate.opsForValue().set(keyPrefix+id,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //6.存在，将数据写入redis中
        this.set(keyPrefix+id,r,time,unit);
        //7.返回
        return r;
    }



    //线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR= Executors.newFixedThreadPool(10);
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key,"1" ,10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }
    //逻辑过期解决缓存穿透查询
    public <R,ID> R queryWithLogicalExpire(
            String keyPrefix,ID id,Class<R> type,Function<ID,R> dbFallback,Long time, TimeUnit unit){
        //1.从redis中查询缓存
        String json = stringRedisTemplate.opsForValue().get(keyPrefix+id);
        log.info(json);
        //2.判断是否存在
        if(StrUtil.isBlank(json)){
            //3.不存在，直接返回
            log.info("不存在");
            return null;
        }
        // 4.命中,命中需要吧json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        R r = JSONUtil.toBean(data, type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            //5.1未过期直接返回店铺信息
            log.info("未过期");
            return r;
        }
        //5.2过期，需要缓存重建
        //6.缓存重建
        //6.1 获取互斥锁
        String lockKey=LOCK_SHOP_KEY+id;
        boolean isLock = tryLock(lockKey);
        //6.2 判断是否获取互斥锁成功
        if(isLock){
            log.info("获取互斥锁成功");
            //6.3 成功,开启独立线程实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //重建缓存
                    R r1 = dbFallback.apply(id);
                    log.info("准备获取过期时间");
                    this.setWithLogicalExpire(keyPrefix+id,r1,time,unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }
        //6.4 失败,返回商铺信息
        return r;
    }
}
